Corn Earworm
Heliothis zea (Boddie), Noctuidae, LEPIDOPTERA)

DESCRIPTION

Adult - This moth has a wingspan of 25.5 to 38.5 mm. The forewings of the males are usually light yellowish olive; those of the females are yellowish brown to pinkish brown. The covering of the head and thorax match the forewings, and the abdomen is somewhat paler. The hind wings are white with a broad, dark brown, outer marginal band and usually a narrow, brown, intermarginal band.

Egg - The dome-shaped egg is white when first deposited, developing a reddish brown band before hatching. It is approximately 0.5 mm wide.

Larva - There are five to six instars varying from 1.5 to 44 mm in length. Newly hatched larvae are yellowish white with dark head capsules. Second instars are yellowish green and frequently have orange and brown, longitudinal stripes; their head capsules are reddish-brown or brown. Later instars may be greenish-yellow, reddish, or brown with pale, longitudinal stripes, raised black spots (chalazae), and brown to orange heads. All instars have five pairs of fleshy prolegs.

Pupa - The pupa is about 31.5 mm long and 6 mm wide. Initially, a shiny reddish brown, it becomes dark brown when adult emergence approaches.

BIOLOGY

Distribution - The corn earworm is found throughout most of the Western Hemisphere. Frequently encountered in the southern United States, it has been found as far north as Saskatchewan and has been recently introduced into the Hawaiian Islands. In North Carolina, it occurs in virtually every corn field sometime during the growing season.

Host Plants - The corn earworm is found on over 100 host plants, but corn is the preferred host. In North Carolina, it occurs on at least 14 cultivated plants (alfalfa, bean, corn, cotton, okra, peanut, pea, sorghum, soybean, strawberry, sweet pepper, sweet potato, tobacco and tomato). This insect is also found occasionally on wild hosts such as toadflax.

Damage - The corn earworm is one of several caterpillar pests of peanuts. Damage is largely restricted to the foliage although they will occasionally feed on pegs and pods. Infestations generally occur from mid-August to October.

Life History - In North Carolina, the corn earworm overwinters as a "resting" (diapausing) pupa in the soil at a depth of more than 50 mm. Adults emerge in early May, mate, and seek suitable host plants where the females deposit their eggs singly. Each female may lay from 450 to 3,000 eggs which usually hatch within 3 days.

In spring, because no single host is both abundant and in a stage attractive enough to receive a majority of eggs, moderate numbers of larvae occur on several hosts. When field corn starts silking, most of the eggs are deposited on corn. Later in the season, when corn silks dry, this pest lays eggs on a variety of hosts such as cotton, soybeans, certain vegetables and peanuts. The corn earworm usually does not appear in peanut fields in large numbers until after both corn and cotton begin to mature. Up to four generations occur each year in North Carolina, but the third generation is of most significance to peanuts.

CONTROL

For control recommendations, consult the current North Carolina Agricultural Chemicals Manual.